Roberta Wohlstetter: WSJ celebrates her work on Pearl Harbor

When Roberta Wohlstetter set out, in the early 1960s, to explain why the U.S. had been surprised by the Japanese attack on Pearl Harbor, she confronted a puzzle that to some seemed like a conspiracy.

Unlike classic military surprises, the U.S. had received ample intelligence that the Japanese were prepared to attack the Hawaiian base. That nothing was done to remove American ships to safety was proof, for Clare Booth Luce among others, that Franklin Roosevelt had "lied us into war because he didn't have the courage to lead us into it." But Wohlstetter, who died Saturday at age 94, knew better, and she spelled it all out in "Pearl Harbor: Warning and Decision," perhaps the most important book ever written on military intelligence.

Yes, the U.S. had intelligence that Pearl Harbor was a potential Japanese target. But other intelligence suggested Siberia could be a target, or the Panama Canal, or the Philippines. Previous indications of an impending attack had served, like so many false alarms, to lower America's guard. And American planners had trouble believing the Japanese would launch a war against the United States that they couldn't possibly hope to win.

From this, Wohlstetter drew the essential conclusion that the U.S. failed to anticipate the attack on Pearl Harbor because, amid mountains of incomplete and often conflicting data -- what she called "noise" -- intelligence analysts couldn't distinguish the information that really mattered. This tended to lead, as the future Nobelist Thomas Schelling wrote in his preface to Wohlstetter's book, to "a routine obsession with a few dangers that may be familiar rather than likely."

The lessons are timeless, and foretold the findings of the 9/11 Commission. Contrary to the views of many so-called realists, nations do not always act from rational calculations of their self-interests: They can be reckless gamblers, something that should give pause to those who see nothing to worry about in the prospect of an Iranian nuclear weapon. And contrary to the instincts of many CIA "professionals," the best intelligence analysis requires judgment and imagination, not simply the widest possible data set.

Wohlstetter was also remarkable not simply as a woman working in what was then a "man's field," but also as the wife and intellectual partner of the late Albert Wohlstetter, the legendary nuclear-strategy theorist. Both Albert and Roberta were great friends of this page, as well as great patriots.